Tub-to-Shower Conversion: Curbless Is Rare, Not like the Ads

You are tired of stepping over the side of the tub, and you want a walk-in shower that looks good and works every day. The ads make it sound simple: one day, one crew, done. What they leave out is the part we see on almost every job, which is what turns up behind and under the old tub.

Here is what a real tub-to-shower conversion involves, what it costs you in time, and the honest answer on curbless showers.

What we find when the old tub comes out

Almost every time we pull a tub for a walk-in shower conversion, we find water damage. Many times, we find wood rot and poor framing and hidden plumging problems. Sometimes it is a stained subfloor and some soft drywall. Sometimes it is extensive wood rot and mold.

The water gets in from a few predictable places:

• The plumbing itself. Small, slow leaks at the pipes, around the shower valve, or around the tub spout. They drip inside the wall for years and nobody sees them.
• The tile surround. Water works through cracked grout and tile and into the wall cavity around the tub. Grout is not waterproof, and a tile wall is only as dry as what sits behind it.
• The bathroom floor. Water that splashes or drips onto the floor outside the tub soaks into whatever flooring is there and works down into a wood subfloor.

In a house on a raised (pier-and-beam) foundation, or a bathroom on a second floor, the damage can reach the wood subfloor and the structure below it: the framing underneath, or the floor joists. In the bad cases we see rot in the lower two feet of the wall framing, and it can run into the room next door.

One of our jobs, after the tub came out: the dark staining on the lower wall and the wet slab are water that had been getting behind the tub for years.

None of this shows from the bathroom. It only shows once the tub and the surround are out, which is exactly why it matters how the new shower goes in.

There is no such thing as a one-day shower

The "one-day shower" in the ads is not one day. A crew still has to come out, disconnect the plumbing and demolish the tub and surround. Then a licensed plumber has to do the new plumbing and then the preparation for the new shower. The "one day" is the last step: a fiberglass shower pan and three composite wall panels...Not a custom tiled shower.

That is a walk-in shower, and for some homes it is a reasonable budget option. But it is not a curbless shower. And here is the problem with doing it fast: if there is rot behind the old tub, the only way to deal with it properly is to open the wall and the floor, dry it out, and replace what is damaged. A process built around gluing panels in on a single day has no time in it for finding and fixing what was behind them.

A real tiled shower conversion usually takes about two weeks. That time goes on the parts you never see: demolition, repairing any water damage, plumbing, framing, waterproofing, and tile.

Curbless showers: the honest answer

Curbless (also called zero-entry) showers are what most people picture: the bathroom floor runs straight into the shower with nothing to step over. They look great in photos. In a lot of houses, they are not very practical, and in some they are not possible without major work.

The reason is the drain. A shower floor has to slope to its drain, and a curbless shower needs that slope to start below the level of the bathroom floor. In a new build today, many builders leave a recess in the concrete slab for it. In an existing Southwest Austin home, that recess is almost never there, whether the house sits on a slab or on piers and beams.

The way around it is to cut the slab out where the shower will go and lower it two to three inches, so the shower pan sits below the bathroom floor and the two meet seamlessly. We have done it. It is a lot of work, and it typically adds a couple of thousand dollars to the project.

On a raised, pier-and-beam foundation it is no easier. Dropping the subfloor to recess the shower pan means cutting into floor joists and structural beams, and that usually means bringing in a structural engineer. It typically adds around $3,000 to the project compared with a low-curb shower.

Even done well, a flush, curbless pan is difficult to get right. Get the slope or the waterproofing slightly wrong and the water does not stay in the shower. There is nothing at the edge to hold it back from the rest of the bathroom.

Why a low curb is usually the better shower

For most conversions we recommend a walk-in shower with a very low curb, around two inches off the floor. That is low enough to step over easily, with no climbing in and out the way you do with a tub. It also holds the water in, so a long shower never means a wet and dangerous bathroom floor.

Remember where the rot came from: water reaching the floor outside the tub. A low curb with proper waterproofing behind the tile is how you stop that happening again.

If curbless is what you want, and your house can take it, we will tell you what it involves for your floor before anything is cut. In many homes, though, a well-built low-curb shower gives you nearly everything a curbless one does, for less cost and less risk.

What a properly built conversion includes

When we convert a tub to a shower, the work generally runs in this order:

1. Demolition. The tub, the tile surround and the wall board come out, down to the framing.
2. Repair what we find. Any rotted framing, subfloor or structure gets replaced before anything new goes in. This is the step that cannot be skipped, and the one a fast install has no room for.
3. Plumbing. We replace all of it: the valve, the supply lines, the drain and the drain flange that ties it into the shower floor and waterproofing. The drain gets moved and centered. We do not leave an old valve or old shower plumbing behind brand-new walls, where the next leak would start out of sight. New work gets high-quality valves and fixtures, through our plumbing team.
4. Framing and blocking. While the walls are open, we add solid wood blocking where a grab bar or a shower seat might ever go, even if nothing is being installed now. If you or anyone else wants one later, it can go in without opening the tile, and it will be anchored into something structural. We do the same for shower glass: framing in the walls for a glass door or panel, even if you are choosing a curtain now, so glass can be added later by you or whoever owns the house next.
5. Lighting. Most bathtubs have no light over them, so a walk-in shower can feel like a dim box. We usually add a recessed light in the center of the new shower ceiling, rated for wet locations, through our electrical team.
6. Waterproofing. We are very big on this. We use the Schluter Kerdi system, or a system like it: a continuous waterproof membrane behind the tile and under the shower floor. This, not the tile, is what keeps the water out of the walls.
7. Tile, glass and fixtures. The part you see, and the part most people spend their time choosing.

Which drain to choose

We usually put the drain in the center of the shower floor, or slightly off-center toward the shower head, where most of the water lands.

Linear drains, the long narrow channels along one edge, look really sharp in photos. In our experience they do not drain as well, and they are very modern: a lot of people who choose one end up not liking it. We can install them, but we recommend against them for most homes.

Permits in Austin

If your home is inside the City of Austin, a major bathroom renovation like this needs a permit from the City's Development Services Department. Moving plumbing and opening walls and floors is not a cosmetic job. A permitted job also leaves a record that the work was inspected, which matters when you sell.

Outside the city limits, rules depend on where the property sits, so ask before work starts rather than assuming.

Glass, curtains and hard water

Around here, everyone has hard water. Limestone puts a heavy mineral load in it, and that load ends up as white spots and haze on shower glass, and as scale in shower heads and valves.

If you want a glass door or glass walls, we recommend ShowerGuard glass from Guardian, which has a permanent coating that resists the etching and clouding hard water causes. It comes with a manufacturer's warranty; ask for the current terms when you choose it. Even so, without a water softener, glass in a Hill Country shower is no fun to keep clean.

A shower curtain is a perfectly good answer, and plenty of people prefer it. Some simply do not like the idea of a glass panel in a wet room, and a curtain is easy to clean, easy to replace, and keeps the shower open and easy to step into. Pair it with the low curb and it keeps the water where it belongs.

What to ask before you sign anything

• What happens if you find water damage once the tub is out, and how will you tell me?
• Is the shower tiled over a waterproofing membrane, or panels glued to the wall?
• Will you replace the valve and the shower plumbing, or reuse the old ones?
• Does my floor allow a curbless shower, and what would it take?
• How high will the curb be?
• Glass or a curtain, and if glass, what keeps hard water from clouding it?
• Will this need a permit at my address?

If the answer to the first question is vague, that is your answer.

We do these conversions as part of our bathroom and remodeling work, and they are one of the most common changes people make to stay comfortable in the home they love. If you are wondering whether water has already been getting behind your tub, that is something we look at on the first visit too.